PCI: hv: Turn on the host bridge probing on ARM64

Now we have everything we need, just provide a proper sysdata type for
the bus to use on ARM64 and everything else works.

Link: https://lore.kernel.org/r/20210726180657.142727-9-boqun.feng@gmail.com


Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>